CHAPTER XXII 
THE SIMPLEST GREEN PLANTS 
260. Introduction. — Many plants never have more than 
one cell and are so small that they can be studied only 
through a microscope. All these minute plants have long 
scientific names, often hard to remember, but they are the 
same names which the English, German, or Japanese chil¬ 
dren have to learn when they study these plants. 
The two plants discussed in this chapter belong to the 
group known as the Green Algce (Latin, algce, seaweed). 
The names of these two plants 
are Pleurococcus (plu-ro-kok'us) 
and Spirogyra (spi-ro-ji'ra). 
We are now to compare these 
microscopic plants with such larger 
plants as lily and nasturtium, each 
of which, composed of hundreds 
of cells, is able to respire, make 
its own food, and produce seeds. 
261. Pleurococcus. — Pleu¬ 
rococcus is a widely distributed, 
single-celled plant which grows in great abundance upon 
the shady side of trees, old buildings, and rocks. After 
a rain it is conspicuous in these places as green patches. 
A bit of this green substance examined with a microscope 
shows many green cells. Each plant or, we may say, each 
cell is a somewhat roundish structure with a clearly defined 
cell wall. The contents of the cell are green, due to the 
chlorophyll which conceals all parts of the cell except the 
nucleus. The nucleus usually lies near the center of the 
304 
a, single plant; b, plant divid¬ 
ing ; c, d, groups of plants. 
